Lettuce

APPEARANCE: Leaf lettuce, as illustrated, comes in many varieties. Leaves vary in shape from broad to narrow, with edges jagged or smooth. Note, however, that all lack distinct leaf stalks (midribs, yes; leaf stalks or petioles, no) and have a rather thin texture. These characteristics together with overall shape distinguish lettuce from other greens, particularly mustard cabbages.

QUALITY: Hot weather and/or old age cause lettuce plants to produce flowers, bitter chemicals, and tough leaves. Logically, then, bunches with short stems, large leaves, and no evidence of flower stalks are the sweetest and most tender.